Nearly half a million people have fled their homes in the Yemeni port city of Hodeidah and surrounding areas since June but fighting has now blocked exit routes, a spokeswoman for the United Nations High Commissioner for Refugees said on Friday

The United States and Britain last week stepped up calls for an end to the nearly four-year war in Yemen that has driven it to the verge of famine, raising pressure on Saudi Arabia as it faces a global outcry over the murder of a prominent Saudi journalist in the Saudi consulate in Istanbul on October 2.

“As testament to how dire the situation is, some 445,000 people from al-Hodeidah Governorate have been forced to flee since June, according to UN data,” spokeswoman Shabia Mantoo told a news briefing.

Some of them have fled to other parts of Hodeidah province and some to other areas of Yemen, she told Reuters.

The province of Hodeidah, including the port city, had a population of 2.6 million in 2011, four years before the civil war erupted, according to Yemeni statistics.

“While the number of those remaining in Hodeidah city is difficult to gauge, UNHCR is worried that people needing to flee for safety aren’t able to do so. They are trapped by military operations, which are increasingly confining populations and cutting off exit routes,” Manjoo said.

U.N. bodies have warned that an all-out attack on the Red Sea city, an entry point for 80 percent of Yemen’s food imports and aid relief, could trigger famine in the impoverished state.

The UNHCR appealed to all sides to allow access to its warehouse stocked with emergency shelter and essential aid items that it said had been cut off by an active front line.

The U.N.’s World Food Programme (WFP) said on Thursday it planned to double its food assistance programme for Yemen, aiming to reach up to 14 million people “to avert mass starvation”.

Saudi Arabia is leading a Western-backed alliance of Sunni Muslim Arab states to try to restore Yemeni President Abd-Rabbu Mansour Hadi and his internationally recognised government that was ousted from the capital Sanaa by the Houthis in 2015.

The United Nations has no up-to-date estimate of the death toll in Yemen. It said in August 2016 that according to medical centers at least 10,000 people had been killed.